1. Field of the Invention
This application relates to the field of speed-responsive engaging devices for hydrodynamic devices.
2. Prior Art
It is known in the prior art to provide lock-up clutches for hydrodynamic devices. More particularly, copending applications, Ser. No. 620,461 filed Oct. 7, 1975, now U.S. Pat. No. 4,049,094 and Ser. No. 700,998 filed June 29, 1976 of common assignee provide clutch mechanisms for hydrodynamic devices having a shoe assembly engaged by centrifugal force and, in addition, engaged by a wedging effect of cam surfaces, and such clutch devices lock together the impeller and turbine elements to improve efficiency by eliminating slippage. Further copending application Ser. No. 732,265 filed Nov. 14, 1976 provides a structure having rollers mounted in the shoe assemblies in engagement with the cams to provide a relatively frictionless engagement between the cam and show assemblies. It has been recognized that the structures of the aforementioned applications as well as the device to be described herein provide solutions to problems encountered with lock-up clutches to provide a lock-up clutch which disengages during torque impulses or torque reversals to provide smooth, shockless operation and eliminate torsional vibrations.
These previous solutions to the torque converter clutch problem, although workable and dramatic improvements over those known prior, have a somewhat sensitive characteristic which can be improved. This characteristic depending upon the angle of the cams used and other dimensional and operational characteristics is that at times the shoe assemblies will tend to be coupled to the drum engaging surface by the viscous drag of oil in the converter housing before the desired time of clutch engagement is reached.